Drawing on OneNote for IOs

I'm ready to give up on OneNote... it used to be good. I have two problems that regularly interrupt my work.

The first problem I noticed was that when I double tap my Apple Pencil, although it is set to go to the eraser, it does that for a brief moment and then turns into that text-to-type pen. 

The second, and more important, problem, is that quite regularly all the drawing pens suddenly are greyed out and there is nothing I can do (other than possibly waiting a long time) to get them working again. 

The first problem I can work with, it's just annoying, the second has got me ready to shift my notes from OneNote.

Has anyone got any suggestions for fixing either of these? The support crew have had me try the same things each week, and none of it works.

Thanks in anticipation!